Salts in connection with other substances including silica are known. U.S. Pat. No. 5,753,345 discloses an adsorber for humidity and odorous gas exchange. A silica sol is coated on a sheet to obtain an adsorbing body. The silica particles have a diameter <120 Å and a plurality of stable silanol radicals on the surface, giving strong binding ability. The silica sol optionally comprises a humidity absorbing agent such as for instance lithium salts, magnesium salts and calcium salts. The silica sol coating is applied on a sheet or a laminate and dried to gelatinize it and is then rigidly fixed on said sheet or laminate.
Tablets of salts together with binders are also known. US 2006/0097223 discloses a device for controlling relative humidity with a solidified humectant composition. The solidified humectant composition is made from a humectant salt, water, and a carrier. The solidified humectant may be formed into a tablet with the aid of a binder, or it may be contained within a thermoformed felt material, a sachet, or a water permeable canister. Examples of salts include CaCl2, K2CO3, LiCl2, NaCl, and K2SO4. Examples of carriers include silica gel.
The principle of the operation of chemical heat pumps is well-known, see for example U.S. Pat. No. 5,440,889, U.S. Pat. No. 5,056,591, U.S. Pat. No. 4,993,239, U.S. Pat. No. 4,754,805 as well as U.S. Pat. No. 6,634,183. Many chemical heat pumps comprise at least one salt as an active substance and at least one liquid. In U.S. Pat. No. 6,634,183 there is described a solid phase of an active substance primarily located inside a net, while a solution phase is able to pass the net. There is further provided distribution means such as a pump to make the separated active substance in liquid state or solution phase pass in contact with a heat exchanger and the active substance in solid state.
A drawback relating to the use of salt solutions in absorption processes is that corrosion easily occurs. Corrosion typically results in the formation of non condensable gases, mainly hydrogen gas (H2), or even rupture of the building material in a machine working according to the absorption process. The effects of corrosion gases decrease or stop the absorption process. A problem in connection with corrosion is that hydrogen gas has to be purged from the system.
In known absorption processes, the problem of corrosion is difficult to solve since corrosion can only partly be inhibited by for example the addition of different corrosion inhibitors, adjustment of the pH or by choosing a corrosion resistant material from the group of noble, and thereby expensive, metals.
US 2002/0043649 describes an effort to control the corrosion in heat pumps by adding a rare earth metal salt to the heat pump's ammonia/water working fluid. In preferred embodiments, the rare earth metal salt includes cerium, and the steel surfaces are cerated to enhance the corrosion-inhibiting effects.
Although chemical heat pumps working in accordance to the hybrid principal and involving a matrix are used successfully today, see for example PCT applications WO 2007/139476 and WO/2009/102271, the long term stability can still be improved. Sometimes, liquid migration of the salt inside the matrix may occur over long periods of time. This salt migration causes an uneven salt concentration in the matrix, resulting in a decreased performance of the machine. Moreover, in such a machine, salt can also migrate in liquid droplets with the gas flow and thereby slowly contaminate the condenser/evaporator. This affects the performance of the heat pump negatively. Thus, regarding the long term stability there is room for improvement.
Yet another problem with chemical heat pumps working in accordance to the hybrid principle involving a matrix is that the matrix material itself may be of a corrosion sensitive material. The corrosion of the matrix may result in general corrosion related problems such as release of corrosion gases but it may also result in the degradation of the matrix, an unwanted side effect.
In chemical heat pumps working in accordance to the hybrid principle involving a matrix, the gas transport during charging and discharging is reduced by salt water solution blocking the gas channels in the matrix. It is desired to reduce or eliminate this problem.
In chemical heat pumps working in accordance to the hybrid principle involving a matrix, the volume of the gas channels in the matrix vary depending on the amount of liquid absorbed in the matrix, this variation may lead to unwanted effects. It is desired to reduce or even eliminate this problem.
In chemical heat pumps working in accordance to the hybrid principle involving a matrix or working according to principals of falling film it is always beneficial for good performance to have a great surface contact between the gas phase and the salt. This is valid both during charging and discharging. Thus it is desired to increase the contact area between a gas phase and a salt in a chemical heat pump working according to the hybrid principle. In the present chemical heat pumps working in accordance to the hybrid principle there is room for improvement regarding the surface area.
“Dry water” is a known material comprising water and hydrophobic nanoparticles. The material is a free flowing powder that is prepared by mixing water, hydrophobic nanoparticles, e.g. silica derivatives such as silica dimethyl silylate, and air at high speeds. The mixing at high speeds results in a water-in-air emulsion, creating particles where the nanoparticles are arranged enclosing small water droplets, acting as a barrier between the environment and water. The water droplets are separated and prevented from fusing. The emulsion formed is dry and can be poured as a free flowing powder. The concept of dry water and how it is made has been known since the 1960's, see for example U.S. Pat. No. 3,393,155 and U.S. Pat. No. 4,008,170, however in recent years dry water has regained interest. Application areas for dry water have for example been mentioned to be an ingredient in cosmetics, for storage of gases or for speeding up catalytic reactions. One problem with structures made of dry water is that they tend to collapse when they are heated so that the water evaporates. Thus it is difficult to obtain a fully reversible process.
In the prior art there is further a need for an energy carrier which is easy, simple and economical to transport.